#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i,j;
    int x = 5;
    int y = 10;
    
    int hight = 20;
    int velocity = 1;
    
    while (1)
    {
        x=x+velocity;
        system("cls");   
        
        for(i=0;i<x;i++)
            printf("\n");
        for (j=0;j<y;j++)
            printf(" ");
        printf("o");  
        printf("\n"); 
        
        if (x==hight)
            velocity = -velocity;
        if (x==0)
        {
            velocity = -velocity;
        }        
    }    
}
